Every airplane generates wake turbulence when airborne. The lift that's produced creates vortices that counterrotate and trail behind the aircraft. The vortices are formed as air that was compressed beneath the passing wing mixes into lower-pressure air that passed above the wing.

Wake turbulence is what happens when an airplane encounters a lingering vortex, and its magnitude ranges from a barely perceptible bump to involuntary, violent aerobatics. A smaller aircraft that encounters the wingtip vortices produced by a larger aircraft may roll excessively, making it difficult for the pilot to maintain control. At low altitude, on final approach, an encounter with wake turbulence can be catastrophic.

The intensity of the wake turbulence that’s produced is at its highest when the aircraft producing the vortices is heavy and slow. So, although all aircraft generating lift also generate wake turbulence, it becomes a serious safety issue when a smaller aircraft follows a larger aircraft.

Air traffic controllers are trained to allow for wake turbulence when spacing aircraft arrivals and departures, and advise pilots who are likely to encounter it. For example, controllers are required to wait three minutes before clearing an aircraft to take off behind a heavy aircraft. However, the pilot in command always has the final authority and responsibility for the safety of the flight. And that would also include requesting a delayed takeoff, a go-around, or any other adjustment if they think it's needed.

When taking off behind a heavier aircraft, pilots must be aware of the point of rotation. That’s the point at which lift generation begins and wake turbulence is first produced as a result. Since the turbulence that’s created sinks, aircraft that follow can avoid that wake turbulence by taking off before they reach the point of rotation and climb above the prior aircraft's flight path.

At the end of the flight, wake turbulence is generated until the point the aircraft touches down. When flying a smaller aircraft arriving behind a larger aircraft, the pilot should note the touchdown point for the aircraft they're following. They can avoid the wake turbulence by staying slightly above the flight path and landing beyond the larger aircraft's point of touchdown.

Also, keep in mind that wind can displace the vortices, so caution must be exercised when landing or taking off on parallel runways, for example.

More information about wake turbulence can be found in Chapter 7 of the Aeronautical Information Manual and in FAA Order 7110.65BB, "Air Traffic Control."